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11. Human and Environmental Toxicology
- Indiana University Press
- Chapter
- Additional Information
11 Human and Environmental Toxicology Many people live in close proximity to lewisite deposits in the United States, Russia, and China. Are these individuals at increased risk for contracting life-threatening illnesses? Similarly, do the great quantities of lewisite that have been dumped in bodies of water around the world constitute a hazard for animal (especially marine) and/or human life? The answers to these two questions are, in turn, based on two additional questions: What are lewisite’s degradation products, and how toxic are these products? Unfortunately, the answers to these two questions are dependent on many factors, making absolute determinations of risk impossible . The degradation of lewisite both on land and in water has been inadequately investigated, and the studies that have been performed have produced confusing and contradictory conclusions. Still, some facts are known, perhaps the most important of which is that lewisite breakdown products contain arsenic. As discussed previously, in the presence of moisture lewisite rapidly undergoes hydrolysis. This reaction results in the formation of chlorovinylarsonous acid and hydrochloric acid; it proceeds very quickly and is reversible. In the presence of additional quantities of water, the hydrolysis reaction will continue resulting in chlorovinylarsonous oxide (CVAO; see appendix 3). CVAO is a white powdery substance that is poorly soluble in water. Thus, if an area in which lewisite was deposited was at ¤rst very moist and then dries, the resulting lewisite degradation product will most likely be a very stable dry white powder that is easily carried by the wind and that can be ingested by a children putting dirt in their mouths. Further chemical degradation, especially in soils that are high in pH (alkaline soils), may occur, resulting in inorganic arsenic compounds. In seawater, lewisite degradation produces both organic and inorganic arsenic compounds. In addition to concerns about lewisite’s breakdown products, whenever lewisite is manufactured, substantial quantities of arsenic-tainted waste products are also produced, especially associated with the catalyst (typically aluminum or mercury chloride; see appendix 2 for more details). The toxicity of arsenic compounds varies. Thus, to determine the precise health risks of a lewisite-contaminated area, it is essential that the speci ¤c degradation compounds be known. Unfortunately, because of inadequacies in chemical analysis or ¤nancial considerations, this is rarely the situation. Nevertheless, it is possible to describe some general symptoms associated with arsenic toxicity. Ingestion of a large quantity of arsenic results in a metallic taste in the mouth and excessive salivation within about thirty minutes. Subsequent symptoms include vomiting, perspiring, a garlic-like breath odor, and diarrhea . Finally, seizures occur, and death follows from generalized organ failure due to low blood pressure. This occurs because of decreased blood volume when excessive amounts of blood plasma escape from arteries and veins. Similar symptoms of acute intoxication are caused by arsenic entering the body by other routes (surface contact or inhalation), although higher levels of exposure are required to produce symptoms equal to those produced by arsenic ingestion. It is possible for people living near lewisite-contaminated sites or storage facilities to suffer from the symptoms described above—but that would require direct exposure to lots of lewisite residues. It is more likely that people living near lewisite-contaminated areas would be exposed to relatively chronic, low dose levels of arsenic, through either inhalation (e.g., of dust containing arsenic), skin contact, or ingestion of drinking water. The deleterious health effects caused by chronic arsenic exposure are sometimes referred to as arsenicosis and often do not become evident until after a few years of exposure (e.g., two to ¤ve years). Unfortunately, arsenicosis is endemic in many parts of the world where water supplies are contaminated by arsenic. The most disturbing example is Bangladesh, where thirty-seventy million people currently consume arsenic-contaminated water; the World Health Organization has described this as the largest mass poisoning in history. But other countries face this problem too, including Argentina, Chile, China, Hungary, India, Mexico, Nepal, Pakistan, Thailand, Taiwan, and Vietnam. There are even some localities in the United States where drinking water is contaminated with arsenic. The most common early signs of chronic arsenic poisoning are muscle weakness and aching, increased skin pigmentation, hardening of the skin, and edema (swelling). Other signs are garlic odor of the breath and per144 Dew of Death [3.80.24.244] Project MUSE (2024-03-29 13:04 GMT) spiration, excessive salivation and sweating, generalized itching, sore throat, nasal discharge, lacrimation (tearing of the eyes), numbness, burning or...